1. Field of the Invention
This invention relates to a clutch device for an automatic paper feeder, and more particularly to a clutch device for an automatic paper feeder which transfers rotary driving force from a drive shaft provided in a printer body to a feeding roller through proper timing control.
2. Description of the Prior Art
A typical automatic feeder includes a feeding roller to hold uniform-size sheets of printing paper between a pressure plate and itself, and separates and feeds them one by one to the attached printer through the rotation of the feeding roller. To avoid possible paper skew and other problems during the feeding operation, for example, a normal rotation feeding clutch mechanism as disclosed in the Japanese Utility Model Application Laid-open No. 163332/1987 is adopted in the feeder. That normal rotation feeding technique is intended to separate and feed the sheets of paper installed in the feeder one by one to a platen of the printer by rotating the feeding roller simultaneously with the normal rotation (the rotation in the feeding direction) of the platen. During the separation and the feeding before the sheet is caught by the platen, the sheet may slant against the feeding direction for some reason, which is called skew. To avoid this skew, when the front edge of the sheet reaches the platen, that technique stops the feeding roller and at the same time, reversely rotates the platen to provide a flexure with the sheet, and then normally rotates the platen for feeding.
When the normal rotation feeding technique described above is used to avoid skew, the printer is required to include a controller which controls the timing for switching the platen rotation from normal to reverse and then to normal, and its clutch mechanism is required to include an origin detecting mechanism which cooperates with the controller. Moreover, the control operation is quite complicated because proper timing control is indispensable for driving and stopping the feeding roller.
Accordingly, the prior automatic feeder using the normal rotation feeding technique must have a complicated controller in the printer body to control the feeder, and the clutch mechanism must consist of many parts. These requirements make the feeder very heavy and expensive.